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Capturing age and sex of subjects from whole-body features has important applications in a wide variety of areas. However, current techniques for determining this information without subject interaction or high-resolution images are problematic. While computer vision techniques (e.g. poselets and histogram-oriented gradients) are functional at a stand-off, these methods often include areas influenced by characteristics such as clothing or hairstyle which vary by region and culture. Whole-body anthropometrics, especially those of children and youth experiencing rapid musculoskeletal changes, may help inform robust models of age estimation and sex classification. Models of anthropometric variables were developed from a pre-existing database for age estimation using linear regression techniques. Sex classification was performed both over the entire subject group as well as three individual age bins (2 ≤ subject age < 8, 8 ≤ subject age < 14, and 14 ≤ subject age). Age estimation models were highly dependent on head size and exhibited r-squared values as high as 0.91 and root mean square error values as low as 1.29 years. Sex classification was found to be highly linked to a combination of foot, hand, hip, and torso metrics for correct classification as high as 88%. The results presented herein may help develop and focus methods of determining age and sex.

Studies on human perception have identified pelvis and torso motion as key discriminators between male and female gaits. However, while most observers would advocate that men and women walk differently, consistent findings and explanations of sex differences in gait kinematics across modern empirical studies are rare. In the present study we evaluated sex differences in whole body gait kinematics from a large sample of subjects (55 men, 36 women) walking at self selected speeds. We analyzed the data through comparisons of discrete metrics and whole curve analyses. Results showed that in the frontal plane, women walked with greater pelvic obliquity than men, but exhibited a more stable torso and head. Women had greater transverse plane pelvis and torso rotation as well as greater arm swing. Additional sex differences were noted at the hip and ankle. These kinematic results are in line with anectdotal observations and qualitative studies. In order to understand these observations and substantiate some of the explanations previously set forth in the biomechanics literature, we also explored possible reasons for dynamic sex effects, and suggested applications that may benefit from their consideration.

Tarsometatarsal (TMT) dislocations are an uncommon but debilitating athletic injury. When symptomatic midfoot instability persists, an injured athlete frequently requires surgical stabilization and rehabilitation for up to 9 months before returning to full athletic participation. Unfortunately, the limited biomechanical knowledge of this injury prevents prophylactic measures from being developed that could reduce an athlete's risk of injury. The goal of this article is to summarize the literature on TMT dislocations, with a particular emphasis on the relevant biomechanics, in an attempt to clarify the circumstances and mechanisms under which these injuries occur. Since athletic injuries represent only a small portion of all TMT dislocations, other categories of injuries are also considered for the insight they provide. This review first summarizes the anatomy of the TMT joint as well as the clinical details surrounding TMT dislocations. The various hypothesized injury mechanisms are then reviewed with particular attention given to cadaveric studies that investigate these mechanisms. Based on this critical review, gaps in the research related to epidemiologic data, full-scale and component testing, numerical modeling, and countermeasure development, are identified. Only by improving our understanding of the causes and biomechanics can steps be taken to protect athletes from these injuries.

The purpose of this study was to describe stance foot and ankle kinematics and the associated ground reaction forces at the upper end of human performance in professional football players during commonly performed football-specific tasks. Nine participants were recruited from the spring training squad of a professional football team. In a motion analysis laboratory setting, participants performed three activities used at the NFL Scouting Combine to assess player speed and agility: the 3-cone drill, the shuttle run, and the standing high jump. The talocrural and first metatarsophalangial joint dorsiflexion, subtalar joint inversion, and the ground reaction forces were determined for the load bearing portions of each activity. We documented load-bearing foot and ankle kinematics of elite football players performing competition-simulating activities, and confirmed our hypothesis that the talocrural, subtalar, and metatarsophalangeal joint ranges of motion for the activities studied approached or exceeded reported physiological limits.

As social beings, much of our everyday lives are spent in interaction with others, yet the vast majority of gait studies examine solo walking without any distraction. It is largely unknown how walking in a dyad, both with and without talking, affects gait speed, cadence, and step length of adults; however, these same metrics dictate design parameters for widely varying fields from rehabilitation goals and ergonomic environments to animation models and surveillance objectives. This study examined the differences in spatiotemporal metrics between solo and paired walking for same- and opposite-sex pairs while using talking as a method of distraction. Results from 12 female-female (F-F), 10 female-male (F-M), and 12 male-male (M-M) pairs were analyzed. Significant changes from solo walking were only found with opposite-sex pairs (p0.05), with women (F-M/female) increasing speed and men (F-M/male) decreasing speed. Unlike solo walking, changes in speed during paired walking were driven by alterations to step length with very minimal change in cadence. When subjects were directed to talk while walking, both solo and as a pair, gait speed decreased significantly by 4-5%. Because significant changes were observed in paired versus solo walking, both with and without distraction, there may be reason to reevaluate and develop environment-specific rehabilitation goals and normative metrics.

This study investigates the peak force and force at fracture in the patella complex from an axial load similar to that of a knee bolster impact during a frontal automobile collision. A rigid impactor and a 689 kPa padded impactor are used to compare the mechanical behaviour of ‘older’ (mean = 74 years) and ‘younger’ (35 years) post-mortem human surrogate (PMHS) populations. Age-related differences in peak forces and fracture patterns were observed using both impactors, and we hypothesise that the stiffer response of the patella complex in the 74-year-old PHMS group is responsible for these differences. Furthermore, four fracture detection methods (acoustic sensors, strain gauges, piezo-electric sensors and accelerometers) were investigated; the acoustic sensor was found to give the most useful crack detection data. These experimental results can assist numerical modelling and design efforts aimed at reducing the incidence and severity of automotive-related knee injuries.

The common perception that men and women walk differently has been supported by studies in psychology and human perception; however, in modern empirical kinematic studies, sex differences are surprisingly limited, contradictory, or equivocal. Interest in sex differences spans many fields, from psychology to medicine to surveillance. In this review, we assemble and analyze what is known about spatiotemporal and kinematic variables of female and male gait. Historical perspectives, which indicate that sex is identifiable from point-light walkers, are briefly canvassed to help guide identification of structural and kinematic differences. Both spatiotemporal and kinematic data from the past three decades are then presented and discussed. We further analyze the published data in order to identify how height-normalization may affect noted spatiotemporal differences between the sexes. Subsequently, gaps in published data, and the implication of such missing information on gait analysis, are identified. From the analysis performed herein, we suggest that the pooled literature indicates that gait speed decreases with age, and, furthermore, decreases more for women than men. The meta-analysis of spatiotemporal variables normalized to height implies that step length is height-dependent, and, when height-matched, women may walk at a slightly faster preferred speed than men. The compilation of kinematic data suggests that coronal plane pelvis and hip range of motion may be different between the sexes. However, further investigation is needed on nearly every body segment, with special attention to the torso and upper extremities, to explain and quantify or refute gait differences as identified through perception and psychology literature.

FRIMENKO, R. E., W. B. LIEVERS, P. O. RILEY,J. S. PARK,M. V. HOGAN, J. R. CRANDALL, and R. W. KENT.Development ofan Injury Risk Function for First Metatarsophalangeal Joint Sprains. Med. Sci. Sports Exerc., Vol. 45, No. 11, pp. 2144–2150, 2013.Introduction: Sprains of the first metatarsophalangeal (1MTP) joint, also known as turf toe, are debilitating athletic injuries. Because85% of 1MTP sprains result from excessive hallux dorsiflexion, interventions that limit motion to subinjurious levels would greatlybenefit athletes. Hallux dorsiflexion range of motion (hdROM) cannot be overly constrained, however, lest athletic performance becompromised. Therefore, the tolerance of the 1MTP joint to excessive dorsiflexion injury must be quantified before appropriatehdROM limitations may be developed. The purpose of this study was to develop a quantitative injury risk function for 1MTP sprainson the basis of hallux dorsiflexion angle. Methods: Twenty cadaveric limbs were tested to both subinjurious and injurious levelsof hallux dorsiflexion. Motion capture techniques were used to track six-degree-of-freedom motion of the first proximal phalanx, firstmetatarsal, and calcaneus. Specimens were examined by physicians posttest to diagnose injury occurrence and ensure clinical rele-vance of the injuries. Results: A two-parameter Weibull hazard function analysis reveals that a 50% risk of injury occurs at 78- ofdorsiflexion from anatomical zero. Conclusion: Methods presented here drove cadaveric 1MTP joints to various degrees ofdorsiflexion, resulting in both noninjurious and injurious trials, which were formed into an injury risk function. Key Words: TURFTOE, EXCESSIVE DORSIFLEXION, MOTION CAPTURE, HALLUX

Sprains of the first metatarsophalangeal (MTP) joint, referred to colloquially as "turf toe," are a debilitating sports injury because the hallux is pivotal to an athletes' ability to accelerate and cut. Severe sprains may require weeks to full recovery, and injuries requiring surgery may prevent an athlete from full athletic participation for months. Whereas the diagnosis and treatment of turf toe are well documented in the literature, less is known about the biomechanics of this joint and the mechanical properties of the structures that compose it. Nevertheless, this information is vital to those, such as equipment designers, who attempt to develop athletic footwear and surfaces intended to reduce the likelihood of injury. To that end, this review summarizes the literature on the anatomy of the first MTP joint, on biomechanical studies of the first MTP joint, and on the incidence, mechanisms, and treatment of turf toe. Furthermore, gaps in the literature are identified and opportunities for future research are discussed. Only through a thorough synthesis of the anatomic, biomechanical, and clinical knowledge regarding first MTP joint sprains can appropriate countermeasures be designed to reduce the prevalence and severity of these injuries.

Background The causes and mechanisms of tarsometatarsal (TMT) dislocations are poorly characterized. Unfortunately, the rarity of these injuries makes it difficult and costly to gather the epidemiological data needed to better understand the populations at risk and the circumstances under which injury is most likely to occur. Methodology To address this issue, literature reports of TMT dislocations were identified and analyzed to generate statistical descriptions of the common causes of injury, the age and sex of those injured, and the pattern of injury. Over 2000 injuries were identified from 187 articles. Results The analysis reveals that over 40% of injuries were related to traffic accidents. Based on the Hardcastle classification system, more than 60% of TMT dislocation were partial (type B) injuries. Over 55% of the injured were between 15 and 35 years of age, and males were injured more than twice as frequently. Conversely, the victims of falls tended to be older and represented a larger proportion of females. The age and sex of those injured by TMT dislocations vary by cause. Conclusion An improved understanding of the epidemiologic patterns will benefit research into the mitigation and prevention of these injuries.

Background: Tarsometatarsal (TMT) dislocations are uncommon yet debilitating athletic injuries, particularly in American football. To date, the mechanisms of athletic TMT dislocation have been described only anecdotally. This lack of information confounds the development of preventative countermeasures. Purpose: To use video analysis to provide direct, independent identification of the etiologic and mechanistic variables responsible for TMT dislocations in professional football players. Study Design: Case series; Level of evidence, 4. Methods: Sixteen professional National Football League players who sustained publicly reported TMT dislocations were identified. Publicly broadcast game footage of the plays in which injury occurred was reviewed by a panel of 5 biomechanists. Consensus was reached regarding the details surrounding injury, and a weighting was assigned to each detail based on the panel’s confidence. Results: Roughly 90% of injuries occurred while the injured player was engaged with or by another player, a detail that has heretofore been undocumented. Few injuries resulted from direct loading of either the foot or the ipsilateral limb; however, the injured foot was frequently subjected to axial loading from ground engagement with the foot in plantar flexion and the toes dorsiflexed. Injurious loading was often due to external rotation of the midfoot (86%). Fifteen of 16 injuries were season ending. Conclusion: TMT dislocations are frequently associated with engagement by or with a second player but infrequently caused by a direct blow to the foot. Axial loading of the foot, external rotation, and pronation/supination are the most common conditions during injurious loading.